1. Field of the Invention
The present invention relates to a heat exchanger which can be used for a radiator, for example.
2. Description of the Related Art
Conventionally, a heat exchanger includes a plurality of tubes and a plurality of corrugate fins, which are alternately stacked to form a core part. The heat exchanger further includes tanks arranged at longitudinal ends of the tubes. Each of the tanks includes a core plate having tube holes in which the tubes are inserted, and a tank body fixed to the core plate to provide a space in the tank with the core plate. The core plate has a first wall part (tube insertion plate part) having the tube holes. At an outer peripheral portion of the first wall part, a second wall part, which is arranged approximately perpendicularly to the first wall part, is formed. In addition, two inserts (side plates) are arranged at two ends of the core part in a stacking direction in which the tubes and the corrugate fins are stacked.
In such a heat exchanger, when a temperature of a tube 310 is different from those of adjacent tubes, a tube insertion plate part 322 of a core plate 320 may be bent in a longitudinal direction of the tube 310 (direction X), as shown in FIG. 19. Thereby, a stress may concentrate at bases of the tube 310, i.e., end portions of the tube 310 in a width direction (direction Z), which are bending points.
For example, JP-A-2000-213889 discloses a heat exchanger having a plurality of ribs arranged on a first wall part of the core plate approximately parallel to a plurality of tube holes in which a plurality of tubes are inserted. In addition, two ends of each of the ribs are connected to a second wall part of the core plate, for increasing a rigidity of the core plate, and restricting a stress concentration at end portions of the tubes in a tube width direction (tube major direction).
However, when the core plate has the ribs, the core plate is difficult to be deformed in the longitudinal direction of the tubes, thereby a high stress may be generated over the tubes in the tube width direction. In addition, when the ends of the ribs are connected to the second wall part of the core plate, a length of the ribs in the width direction of the tube is long. Thereby, when the core plate is formed by a press working, a formability of the ribs is reduced.
Furthermore, a heat exchanger having a plurality of burring parts J221a is shown in FIG. 20. As shown in FIG. 20, the burring parts J221a are arranged at inner peripheral edges of tube holes J221 in which tubes are inserted, and insert holes J222 in which inserts are inserted. The burring parts J221a have tubular shapes protruding to an inside of a tank. Therefore, the rigidity of a core plate J20 is increased.
Generally, when protruding dimensions of the ribs and burring parts from the first wall part of the core plate are large, the rigidity of the core plate becomes large. However, as the protruding dimensions of the ribs and burring parts are large, the formability of the ribs and the burring parts are reduced.